/Engine/Source/Runtime/Core/Public/Templates/Function.h
We delete the assignment operators because we don't want it to be confused with being related to regular C++ reference assignment - i.e. calling the assignment operator of whatever the reference is bound to - because that's not whatTFunctionRefdoes, nor is it even capable of doing that.
[TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef) & operator= ( const [TFunctionRef](API\Runtime\Core\GenericPlatform\TFunctionRef) & ) const